Fiber spinning with multifilaments

Research effort at Albany International Research Co. has developed unit processes necessary for pilot scale production of several species of reverse osmosis hollow fiber composite membranes. These processes include spin-dope preparation, a proprietary apparatus for dry-jet wet-spinning of microporous polysul-fone hollow fibers, coating of these fibers with a variety of permselective materials, bundle winding using multifilament yarns and module assembly. Modules of the membrane identified as Quantro II are in field trial against brackish and seawater feeds. Brackish water rejections of 94+% at a flux of 5-7 gfd at 400 psi have been measured. Seawater rejections of 99+% at 1-2 gfd at 1000 psi have been measured. Membrane use requires sealing of some portion of the fiber bundle for installation in a pressure shell. Much effort has been devoted to identification of potting materials which exhibit satisfactory adhesion to the fiber while... 

A variation on this approach used multifilament coextrusion, so-called microfabrication by coextrusion (MFCX) . A limitation of the single-filament process is the size of the filament. The rheological properties of the polymer/ ceramic blends make spinning fibers smaller than 250 pm very difficult. Additionally, spooling fine-diameter fibers is quite challenging. The MFCX is shown schematically in Fig. 1.3. The setup is the same as that used to spin fibers except that the spinneret is replaced with an extrusion die with a diameter between 1 mm and 6 mm. Two separate extrusion steps are used. In the first step, coarse primary filaments are extruded from the feedrod (Fig. 

Spinning and Thermosettlng.i i The mesophase pitch is melt-spun in a mono- or multifilament spinneret, heated to 300 - 450°C and pressurized with inert gas. It is drawn at a speed >120 m/min for a draw ratio of approximately 1000/1 to a diameter of 10 -15 jum. The draw ratio is an important factor in the control of the orientation of the fiber structure the higher the draw, the greater the orientation and uniformity. 

Courtaulds Specialty Fibers have developed a X-ray-detectable yarn which is intended for use in surgical swabs. Micropake is a multifilament PP yarn loaded with barium sulphate during melt spinning, and wrapped with a fine polyester. The loading meets the X-ray opacity test requirements of the British Pharmacopeia. Micropake is appropriate for bleaching and steam sterilization and ean be used in woven produets [116, 117]. 

For spinning of the textile PP mono- and multifilaments, the best solution is a laminar crossflow air quench duct with a minimum ratio of air quantity to air velocity. For spinning of fiber staple tows, the crossflowing quench air can be applied for rectangular spinnerets, i.e., inside-to-outside radial quenching, or double-direction turbulence quenching [141]. 

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